In the following description the following abbreviations will be used:    MEN—Metro Ethernet Network    PTP—Precision Timing Protocol (such as described in IEEE 1588v2)    PE—Provider Edge    PDV—Packet Delay Variation    CPE—Customer Premised Equipment    eNodeB—Base station of LTE (Long term evolution 4G networks).Master node and Slave node—network nodes establishing there-between a packet-message stream, for example a PTP stream, mainly for providing the Slave node with timing in reference to the Master node. FIG. 1 (prior art) shows one option of monitoring/measuring parameters of data transmission via a packet-switched network 10, such as MEN. Let us assume that we are interested in providing so-called timing distribution in the network. FIG. 1 illustrates a setup for measuring PDV for an exemplary Ethernet Service being transmitted through a provider network such as MEN 10, between two demarcation points located at two peer elements PE: PE(source) 12 and PE-C 14 (destination, customer side). Peer element 12 may be (or be connected to) a master node such as a node setting time clock which is considered absolute for the network, while peer element 14 may be (or be connected to) a slave node obtaining its time clock with reference to the clock of the master. In other words, timing distribution is being provided throughout network 10. The timing distribution is closely related to monitoring/measuring of packet delays or packet delay variation PDV at slave nodes (say, node 14), with reference to the master node. To measure delays of the Ethernet service in the packet-switched network 10, one may create an Ethernet CFM (Connectivity Fault Management) protocol packet bidirectional stream 11 between the two peers PEs 12 and 14 (e.g., CFM with Y.1731 delay measurement extension of the CFM).
One drawback of such a solution is that, though being sensitive to PDV, the CFM packet stream is different from a PTP protocol pattern. The PTP (Precision Time Protocol) is widely accepted in modern networks and is therefore preferred by the majority of service providers and operators.
Another drawback is that the CFM stream 11 consumes a certain amount of bandwidth BW in the MEN.
As already mentioned, in order to distribute timing (frequency and phase) information in a modern data packet-switched network, it is preferred to use the PTP protocol over the packet-switched network.
FIG. 2 (prior art) illustrates an example of a setup in which a PTP protocol is used for such a purpose in a data packet-switched network comprising MEN 10.
The term “timing distribution” as used herein should be understood for example (but not exclusively), as enabling a time schedule in a cellular network for interaction between cellular base stations in order to regulate time slots of their communication with the users mobile devices.
The PTP protocol is suitable for the above purposes and is thus sensitive to PDV distribution in the network. Therefore it would be reasonable to monitor/measure PDV for a PTP service, e.g. along a network path of the service. Assuming that there is a number of cellular base stations that form a chain in the network, it is accepted in the art that each of these base stations receives its own PTP service from a central (master) node, and monitors the timing distribution (for example, measures PDV) at the site of the specific base station for its specific PTP service. In case the PDV for the PTP service exceeds a desired predetermined value, the operator of the network may wish to receive an indication (alarm) that such a condition had occurred.
The IEEE 1588v2 standard provides a conventional way of monitoring the timing distribution (with measuring delays/PDV), by creating bidirectional data flows specifically dedicated for the purpose of timing distribution. The functionality of timing distribution is conventionally performed by specifically equipped network elements, and such elements—for example, cellular base stations NodeB—usually perform the full set of the required operations (clock+phase recovery, the discussed delay measurement, etc.).
In FIG. 2, the standardized PTP technique orders to launch a PTP data stream 1 between the PTP master node 16 and a first customer node PE-C1 (Slave 1, marked 14). Since slave 1 is connected in chain with Slave 2, a PTP data stream 2 is established between master node 16 and PTP Slave node 2, 20. At least one of the slaves may be implemented in a Customer's Premised Equipment (“CPE”) such as CPE of NodeB. Each of the PTP Slaves 1 and 2 should be able to recover the clock and the phase of the received packets, and to perform necessary PDV monitoring/measurements for the specific respective data streams.
Any additional node (such as node 18 or node 22) in the network would also need timing distribution with reference to the master node 16. It would therefore need to be provided with an additional PTP slave functionality in each of the nodes (Slave 3, Slave 4), and would require establishing an additional PTP service flow for each of the slave nodes (see PTP stream 3 and PTP stream 4).
One of the main drawbacks of the conventional setup illustrated in FIG. 2 is in that the PTP master 16 has to handle an additional Slave function for every additional Slave node, i.e. to create an additional PTP service stream, a task which is not always possible due to a limited number of Slave functions which may be supported by a single PTP Master. Also, every new Master-Slave stream also consumes a certain amount of BW in the MEN.